Normally a data event includes the delta time between itself and the previous data event. But if a write interrupts another write then the event cannot check the timestamp of the previous event and so it uses a delta of 0. Adds a new trace option: force-abs-timestamp. When this is on each event is proceeded by an absolute timestamp event. This follows from a discussion between jbehmer@xxxxxxxxxx and Steven Rostedt found here: https://lkml.org/lkml/2019/5/24/710 Korben Rusek (2): Add force-abs-timestamp trace option. tests for absolute timestamp Documentation/trace/ftrace.rst | 5 + kernel/trace/trace.c | 4 + kernel/trace/trace.h | 1 + tools/testing/selftests/Makefile | 1 + tools/testing/selftests/timestamp/Makefile | 25 +++ tools/testing/selftests/timestamp/abs-test.sh | 156 ++++++++++++++ .../selftests/timestamp/abs-timestamp.c | 198 ++++++++++++++++++ 7 files changed, 390 insertions(+) create mode 100644 tools/testing/selftests/timestamp/Makefile create mode 100644 tools/testing/selftests/timestamp/abs-test.sh create mode 100644 tools/testing/selftests/timestamp/abs-timestamp.c -- 2.27.0.290.gba653c62da-goog
